Just talk about gold and silver instead. Then you can speak in historical terms. Quite frankly, if he doesn't like Bitcoin, and prefers gold and silver instead, then good on him! Let people decide what's best for them.

This is another point. There is no reason for someone to hold something they know will be worth less over time. So no matter what big picture arguments he might provide, just point out that on an individual level, you're just not having it! The individual level is what matters, because if everyone does what's best for them, moving away from an inflationary system is natural.